A critical need exists for a dosage form for the controlled and uniform administration of a drug for therapy over time. Presently, in the practice of pharmacy and medicine a drug is administered in conventional pharmaceutical forms, such as tablets and capsules. These conventional forms deliver their drug by dumping, which leads to uneven dosing of drug and uneven blood levels of drug, characterized by peaks and valleys. Accordingly, this does not provide controlled and uniform therapy over time.
The prior art provides dosage forms for continuous therapy. For example, in U.S. Pat. No. 4,327,725, issued to Cortese and Theeuwes, and in U.S. Pat. Nos. 4,612,008, 4,765,989 and 4,783,337, issued to Wong, Barclay, Deters and Theeuwes, a dosage form is disclosed that provides therapy by generating an osmotic pressure inside the dosage form. The dosage form of these patents operates successfully for delivering a drug for a preselected therapy. With the delivery of some drugs, however, these dosage forms often exhibit erratic release rate patterns, such as a non-uniform variation in the drug release rate, and the dosage form can stop delivering a drug; that is, the dosage form can shut down intermittently.
In view of the above presentation, it is immediately apparent that an urgent need exists for a reliable dosage form. The need exists for a dosage form endowed with properties for delivering a drug at a known and uniform rate over time. The need also exists for a dosage form free of deviation in its release-rate profile, which delivers the needed dose of drug with a reduced amount of drug left in the dosage form at the end of the delivery period. It will be appreciated by those knowledgeable in the drug-dispensing art that if a novel and unexpected dosage form is made available that provides a uniform and known drug-release profile free of the tribulations of the prior art, such a dosage form would represent an advancement and a valuable contribution in the drug dispensing art.